It's an extraordinary publishing phenomenon - atheism sells. Any philosopher, professional polemicist or scientist with worries about their pension plan must now be feverishly working on a book proposal. Richard Dawkins has been in the bestseller lists on both sides of the Atlantic since The God Delusion came out last autumn following Daniel Dennett's success with Breaking the Spell. Sam Harris, a previously unknown neuroscience graduate, has now clocked up two bestsellers, The End of Faith and Letter to a Christian Nation. Last week, Christopher Hitchens' God Is Not Great: How Religion Poisons Everything was published in the US. The science writer, Matt Ridley, recently commented that on one day at Princeton he met no fewer than three intellectual luminaries hard at work on their God books.

This rising stack of books has prompted screeds of debate, flushing out all manner of belief and unbelief in blogs, reviews, essays and internet exchanges in the US. The Catholic columnist Andrew Sullivan has just concluded his exchange with Sam Harris on the net, while the philosopher Michael Novak recently took on the whole genre of New Atheism, or neo-atheism. Surely not since Victorian times has there been such a passionate, sustained debate about religious belief.

And it's a very ill-tempered debate. The books live up to their provocative titles: their purpose is to pour scorn on religious belief - they want it eradicated (although they differ as to the chances of achieving that). The newcomer on the block, Hitchens , sums up monotheism as "a plagiarism of a plagiarism of a hearsay of a hearsay, of an illusion of an illusion, extending all the way back to a fabrication of a few non-events". He takes the verbal equivalent of an AK47 to shoot down hallowed religious figures, questioning whether Muhammad was an epileptic, declaring Mahatma Gandhi an "obscurantist" who distorted and retarded Indian independence, and Martin Luther King a "plagiarist and an orgiast" and in no real sense a Christian, while the Dalai Lama is a "medieval princeling" who is the continuation of a "parasitic monastic elite".

This kind of vituperative polemic sounds a tad odd this side of the Atlantic. Apart from an ongoing anxiety about Islam, the British are pretty phlegmatic about religion. Church attendance continues its steady decline and the Christian evangelical boom has never taken off. The whole New Atheist publishing phenomenon is like eavesdropping on a blistering row in the flat next door: one's response alternates between fascination and irritation, but is it really anything to do with us?

What's clear is that this wave of New Atheism is deeply political - and against some of its targets even a devout churchgoer might cheer them on. What they all have in common is a loathing of an increasing religiosity in US politics, which has contributed to a disastrous presidency and undermined scientific understanding. Dennett excoriates the madness of a faith that looks forward to the end of the world and the return of the messiah. What Dawkins hates is that most Americans still haven't accepted evolution and support the teaching of intelligent design; according to one poll, 50% of the US electorate believe the story of Noah. He argues that "there is nothing to choose between the Afghan Taliban and the American Christian equivalent ... The genie of religious fanaticism is rampant in present-day America."

Harris similarly draws an analogy between Muslims and the American Christian right: "Non-believers like myself stand beside you dumbstruck by the Muslim hordes who chant death to whole nations of the living. But we stand dumbstruck by you as well - by your denial of tangible reality, by the suffering you create in service of your religious myths and by your attachment to an imaginary God."

This is popular stuff - a plague on both your houses - on both sides of the Atlantic after a war on terror in which both sides have used their gods as justification for appalling brutality. But it tips over into something much more sinister in Harris's latest book. He suggests that Islamic states may be politically unreformable because so many Muslims are "utterly deranged by their religious faith". In a another passage Harris goes even further, and reaches a disturbing conclusion that "some propositions are so dangerous that it may even be ethical to kill people for believing them". This sounds like exactly the kind of argument put forward by those who ran the Inquisition. As one New York commentator put it, we're familiar with religious intolerance, now we have to recognise irreligious intolerance.

The danger is that the aggression and hostility to religion in all its forms (moderates are castigated as giving the fundamentalists cover for their extremism) deters engagement with the really interesting questions that have emerged recently in the science/faith debate. The durability and near universality of religion is one of the most enduring conundrums of evolutionary thinking, one of Britain's most eminent evolutionary psychologists acknowledged to me recently. Scientists have argued that faith was a byproduct of our development of the imagination or a way of increasing the social bonding mechanisms. Does that make religion an important evolutionary step but now no longer needed - the equivalent of the appendix? Or a crucial part of the explanation for successful human evolution to date? Does religion still have an important role in human wellbeing? In recent years, research has thrown up some remarkable benefits - the faithful live longer, recover from surgery quicker, are happier, less prone to mental illness and so the list goes on. If religion declines, what gaps does it leave in the functioning of individuals and social groups?

This isn't the kind of debate that the New Atheists are interested in (with the possible exception of Dennett, who in an interview last year was far more open to discussion than his book would indicate); theirs is a political battle, not an attempt to advance human understanding. But even on the political front, one has to question whether all the aggression isn't counterproductive. Robert Winston voiced increasing concern among scientists when he argued in a recent lecture in Dundee that Dawkins's insulting and patronising approach did science a disservice. Meanwhile, critics in America argue that the polarisation of the debate in the US is setting the cause of non-deism back rather than advancing it.

Dawkins is an unashamed proselytiser. He says in his preface that he intends his book for religious readers and his aim is that they will be atheists by the time they finish reading it. Yet The God Delusion is not a book of persuasion, but of provocation - it may have sold in the thousands but has it won any souls? Anyone who has experienced such a conversion, please email me (with proof). I suspect the New Atheists are in danger of a spectacular failure. With little understanding and even less sympathy of why people increasingly use religious identity in political contexts, they've missed the proverbial elephant in the room. These increasingly hysterical books may boost the pension, they may be morale boosters for a particular kind of American atheism that feels victimised - the latest candidate in a flourishing American tradition - but one suspects that they are going to do very little to challenge the appeal of a phenomenon they loathe too much to understand.